hair techniques
polycount lvl 666
just wonndered if anyone had a definitive hair technique.
For short hair cuts i go for the spiky flat top look with lots of alpha 'fan' shapes
For female long hair i have been trying a kind of hair helmet and also tried lots of 'leaves' of hair, raidiating from the crown.
The problems lie with intersection of the leaves, making it look a bit less convincing.
It can easily end up looking like a cheap toupee
I made my hair using surfce tools in max, so i could go back and tweak the shapes easily at spline level.
Anyway, it would be nice to hear some thoughts on hair techniques.
Just to make it clear I am not really stuck on this, just exploring the various options really
For short hair cuts i go for the spiky flat top look with lots of alpha 'fan' shapes
For female long hair i have been trying a kind of hair helmet and also tried lots of 'leaves' of hair, raidiating from the crown.
The problems lie with intersection of the leaves, making it look a bit less convincing.
It can easily end up looking like a cheap toupee
I made my hair using surfce tools in max, so i could go back and tweak the shapes easily at spline level.
Anyway, it would be nice to hear some thoughts on hair techniques.
Just to make it clear I am not really stuck on this, just exploring the various options really
Replies
Here...
http://www.poopinmymouth.com/process/hair_tutorial/hair_01.htm
Looks like its mostly about texturing, but the examples page might give you some ideas if the actual tutorial isn't what you're after.
for long hair i model a guidemesh and use clothsim to shape the planes as desired.
i try to avoid intersecting planes as much as possible. also, having "leaves" sticking out of solid geometry doesn't look convincing for me, so i try to at least hide the seams, snap to edge, face and vertex helps alot in this.
also what i found looks rather horrible is to re-use the same texture snippet and polyplane all the time.
of course, it all depends on what kind of polycount you're working with.
example-pic
yeah as i say its not really about me being stuck here. I have done some pretty decent hair, but I wanted to start a bit of a discussion on this.
I am favouring the modelled hair approach right now, ie geometry to roughly shape the hairstyle and then a few alpha wisps.
Also i will be looking at shaders to get a nice realistic hair texture.
For all I know we might end up developing a hair technique at work so all this will be in vain.
I am thinking along the lines of the mermaid hair in the nvidia demo, which looks pretty nice.
i wonder is this sort of approach will be practical in next gen stuff or will be generally too expensive.
the drawback with alpha mapped planes is the depth sorting issue, especially when several different alphamapped objects overlap. but in some engines is worse enough with only a few layers of alphamas in the scene.
animation-wise the alpha-mapped approach requires a bit more work but produces as very controllable result. in previous tests i've used clothsim to drive bonechains which the hair was constrained to. works well for baking out skeletal animation minus a few issues with animation blending.
the question is if it's cheaper to create hair and animate it via pixelshader or use alpha-mapped geometry that's skinned to bones. seems to me that gfx cards these days have a lot of improvements on the pixel-shader side of things but lack raw poly-pushing performance increases.
anyway, interesting topic.
I suppose there should be some way of labelling each alpha plane, so they are sorted correctly.
Yeah i think no matter how good the shader/technique is, the hairstlye never looks quite natural.
I often think I have done a great technique then it falls down at some point.
hmm so could I make a hair helmet and use reactor to make it fall naturally on to the head?
I have not really used reactor much, so am not sure how far you can go with this.
I am not too conderned about the animation of the hair at the moment, just getting a nice static hairstyle that hangs naturally would be cool
http://media.www.gamestats.com/media/545/545798/img_2970601.html
They use it along with the physics engine and it looks quite nice imo.
It would be cool if they'd make a engine that supports hair like you often see in CG movies (like Final Fantasy), but i think that that stuff might be a bit too expensive. A friend of mine said that Aki's hair was 15000 polys, though, i dont know if this is trustworthy data, but if it is, that is way too much for current PCs even, i think (imagine having 5-10 of those characters on screen
I agree, the hair on Einstein looks very nice, but it's very tedious to make, imo. I might have a take a shot at it soon, myself, as well.
btw. there was a realtime ff demo out there when quadro was introduced. they converted the hair to polygons for an nvidia demo so maybe your friend is right.
well, einstein's hair is really a rather extreme example, "normal" hairstyles are far easier/faster to achieve. i have a pile of those but since the game they were created for is not yet released, i don't fell secure posting them.
sorting alphaplanes manually: done that once, it's only of use for characters which can only been viewed from a certain camera angle. for anything else, the sorting order is incorrect again.
clothsim: what i do is create a mesh that serves as a ground plane and then "sim" planes over it, create offsets and achieve a rather nice non-intersecting bunch of layered planes. i do not use reactor, totally dislike it's "usability". simcloth gives me better feedback and is ok for those simple tasks. max 7.5 and up apparently comes with clothfx.
Its a shame that syflex doesn't come for 3dsmax
are on PC 3d engines, consoles however had never these problems.
In Elder Scrolls: Oblivion they seem to solve this with an CG
Shader the hair on the screenshoots looks nice a thing i like
to know is how the next Unreal Engine solve this or if the
engine solve this, the engine version of UT2004 does an bad
job on this...
It would be cool if they'd make a engine that supports hair like you often see in CG movies (like Final Fantasy), but i think that that stuff might be a bit too expensive. A friend of mine said that Aki's hair was 15000 polys, though, i dont know if this is trustworthy data, but if it is, that is way too much for current PCs even, i think (imagine having 5-10 of those characters on screen ).
[/ QUOTE ]I seem to remember rumours coming out around when the movie was released that the hair took longer than anything else in the movie to render. While that was evidently a hideously inefficient algorhythm, I think we're a long, long way from ever getting anything even slightly like that to render in real time for games.
ruz: i agree, using reactor feels like shooting yourself in the foot - 25 times per second. as i wrote, i use simcloth, which has a realtime preview in the viewport and is quick to set up. you have to grab it from the usual sites though, it's a non-supported freebie these days.
kraftwerk: any technical reasons for consoles to be better at alpha sorting? i can attest that there are sorting problems in metal gear solid and ffx on the ps2, however you have to look out for them since they are few and far between. unreal engine 2 on pc was really nasty at sorting hairplanes, true.
edit: just had a look at this nvidia mermaid demo. the hair is impressive in motion, true. but it's just long, floating hair - they sure didn't have to style a certain haircut, that's where (for me) the problem lies with the "furry" or spline based approaches. only polys give me the neccessary control.
I would love to show it too, but its nda also.grrr
to me that looks like a blend of common alpha mapped polygones and some custom developed stuff that's used to mix in strands of hair. like it can be seen on his moustache and the hair in the neck area. tasty!
There is really only one way to make hair for realtime ( and yes, that includes next gen consoles ) , and that's alpha'd poly strips.
Hair that's pre-rendered is generally procedural curves using a plug-in such as Shag or Shave, or a a proprietary tool. Personally I like Shave because of the awesome styling UI. Ironically I've recently made some geometry hair that was destined for pre-rendering because the procedural hair was taking too long to render and we just didn't have the time. In that instance I used a bunch of alpha'd poly strips with an anisotropic shader. Worked a treat actually.
Actually the fact cloud's hair were confusing me, so I thought what if they had used some alpha maps with an uber high resolution and a anti-aliasing technique (like the anisotropic shader you were talking about).
Thanks for the info tho' may turn useful!
advent children: doubt it. they sit on a pile of technology developed originally for spirits within, they probably use this stuff or an improved version of it. poly planes in motion generate nasty clipping and not the best kind of dynamics, for an extreme close up in a film, that's not enough (imho).
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I think they used alpha, because its faster to render and you get rid of clipping when you clothsim the hair.
thomasp... how are you sorting Einstein's hair? I'd guess your shot is a prerender, not realtime? Manual sorting is a pain in the arse... basically sorting by vertex number right? (lower verts drawn first, etc.). That's the way I've done it, though for simpler things than hair.
i'd love to post pictures but these damn nda's...
sorting hair per hand is impossible imho. it wouldn't look right from different angles. done it once for a model that had to look right from only very few angles and was running in some totally stoneage engine, will never do it again - brrr...!
daz: why should we separate pre-rendered and realtime hair in this thread? both techniques seem very useful for pre-rendered stuff and to me it seems they mixed it in mgs for realtime as well.
toomas: but will the hair motion be as smooth as with a spline based approach? after all you're simming planes, not strands, entirely different shapes. faster to render - i guess that depends. as soon as you're using a whole lot of planes, it get's pretty slow as well, also, at least for me there always was the issue of unrealistic shadow casting with planes.
the main thing i dislike so far with spline based tools is how crude the hairstyling process works. am curious to finally try out shave as soon as max 8 finally arrives.
@thomasp..dont wait for shave.. get ornatrix the syling interface is lightyears beyond shaves.. we has subscription at mythic and i played with a bit.. and i see how when it came out how shave could of been considered a breakthrough but it really seems akward once you have syled with ox that plugin is magic.. and it renders a million times faster than shave..
... work around sorting issues with mulitple draw culls ... they number the layers of hair planes in the order that they will sort ...
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Thanks arshlevon. Yeah, this is the way we do it too. Usually we tell the exporter how many and which chunks of hair to divide the surface into. Then a particular vertex on each surface can be used as the sort position for it, so the surfaces are sorted back to front. Solves most problems, depending on how many surfaces we split the hair/grass/leaves/clouds/etc. into.
But then we're dramatically increasing the number of surfaces that have to be transformed, which can be pretty slow if we have a lot of individual chunks of hair.
I was hoping for some indication of another route, where I could send the hair to the vertex cache as a single chunk of verts.
thomasp, thanks for sharing. I'm wondering if there's something in your pipeline that avoids multiple surfaces being tranformed separately, but still gives you decent sorting of soft alpha?
arshlevon: i've heard of that one, but isn't that most famous for it's crash-happyness? has it really become reliable?
there are also tutorials on the site ,i really recommend checking out the eyebrow tutorial, the sinks are really cool and havent seen anything like them in any other hair system .... my favorite feature is the ability to save complete hairstyles.. even braids and parts.. eveything..and transfer those to ANY character.
I'm thinking maybe the best way to sort soft-alpha is to use separate surfaces only for the highest LOD, then combined as one surface for lower LODs since sorting errors are less noticeable further away (and the alpha can also be mipped down to a harder more-solid gradient, so the translucent texels are even smaller). Hmm, just thinking aloud here, something to play with.
as you can see the hair are pretty awesome, love how they shine
but using multitexturing would not require any sorting, however only works with relative simple meshes...
btw what about pre-sorting for lets say +x +y +z, and some mixed axis, since one could assume you are never inside of the head. and if you are on the opposite site, you could just use the inverse of your precalculated sort order.
then in realtime you find the "best bet" precoded axis... I read somewhere that this is done for trees and alike too. and mostly works. maybe even doing a weighted sum of the sort order based on the closest three sortaxis, dunno might be worth a try
http://pspmedia.ign.com/psp/image/articl...09065803479.jpg
The question now is how do they place them? do they have any procedural technique and stuff or is it all done "by hand"?
btw. i guess AC is intended as a HD release? because that kind of texture resolution doesn't seem to make sense for a DVD only movie.
Anyways what made me think that the hair is alpha is when you look how the long air moves it kinda stretches like cloth. Also look how the ends of the hair fade off.